The present invention relates to high temperature seals of the type used in automobile exhaust systems and, more particularly, to a reenforced exhaust seal capable of relatively noiseless operation.
Typically in the new front wheel drive automobiles, the engine is mounted so that its crankshaft runs transversely with respect to the vehicle body. The exhaust systems for these "transversely mounted engines" include an exhaust manifold pipe which extends downwardly alongside the engine and has a flange at its open end. Due to the normal movement of the engine during operation (resulting from the rotational momentum of the crankshaft and opposing torsional forces of the drive shaft), the exhaust manifold pipe flange reciprocates in such a manner that the central axis of the pipe, which is perpendicular to the plane of the flange, departs from a substantially vertical line and becomes inclined alternately towards the front and rear of the vehicle. It is therefore necessary to use a flexible joint between the exhaust manifold and the tail pipe to absorb this movement which would otherwise be communicated directly to the tail pipe, causing intolerable stresses and strains and resulting in metal fatigue and the accelerated failure of the tail pipe.
It will therefore be understood that with a transversely mounted engine, the exhaust seal in the flexible joint (typically a ball and socket type joint) connecting the exhaust manifold with the tail pipe must be capable of permitting a degree of relative rotation between the exhaust manifold and exhaust pipe and still maintain an effective exhaust gas seal.
U.S. Pat. Nos. 4,417,733 and 4,516,782 describe an exhaust seal in which a flexible sheet of refractory material (graphite in the latter patent) is used to form the rubbing surfaces of the seal, which seal has been found to permit a degree of relative rotation between the exhaust manifold and tail pipe while still maintaining an effective exhaust gas seal. During use of the exhaust seal described in U.S. Pat. No. 4,516,782 as well as other graphite surfaced seals, it has been found that audible sounds or squeaks can be generated as the opposing members of the articulated exhaust pipe joint move with respect to each other and rub against the surfaces of the seal. The audible sounds, while not affecting the actual performance of the seal, can in some circumstances be considered to be annoying.
U.S. Pat. No. 4,601,476 describes an exhaust seal comprising wire mesh and a mixture of metallic fibers, non-metallic filler (such as graphite flakes), a thermally stable lubricant (such as silicone fluid) and resin binder, the mixture surrounding the wires of the mesh and substantially filling the openings in the mesh and forming the seal. The thermally stable lubricant is believed to become coated on the non metallic filler, thereby preventing squeaking of the graphite surface. While such a seal has proven to be substantially squeak free and satisfactory for general use, there are particular high-temperature applications, involving what is believed to be a certain degree of relative rotation between the exhaust manifold and tail pipe, where the longevity of the seal has not proven to be as great as desired. Failed seals have evidenced cracks and wearing away in and about the junction of the inner circumference of the seal and the large flat radial surface thereof.
Accordingly, it is the object of the present invention to provide a reenforced exhaust seal for use in an articulated joint which will not squeak in response to sliding frictional forces resulting from the moving of the joint members, yet prevents exhaust gas leakage.
Another object is to provide such a seal which is reenforced for use in high temperature applications and is not subject to cracking or crumbling during use.
A further object is to provide such a seal which is simple and inexpensive to manufacture.